Vacuum feed carburetor



Nov. 24, 1931. n. F. BRACKE VACUUM FEED QARBURETOR 2 Sheets-Sheet l 7 Filed Dec. 18

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R. F BRACKE VACUUM" FEED CARBURETOR Filed Deo. 18, 192e 2 sneeze-Sheer 2 ne um w vm, w v w @E Ma W Patented Nov, 424, 1931 ILL'IN'oIs, AssIeNon To CURTIS B. curr, TRUSTEE, or

erm-:Neon ILLINOIS ROBERT r. Bmcxn, or cIIIcAGo,

PATENT OFFICE VACUUM FEED l CABBUBETOB Application led December-.18, 1926. Serial No. 155,598.

My invention relates to improvements in vacuum feed carburetors and more particularly that type of carburetor intended for direct connection with the main fuel supply tank of a motor vehicle disposed at or below the plane ofthe carburetor.

It is an object of my invention to provide a carburetor of this type in which the relative levels of the fuel supply tank and the' car buretorwill not affect the uniformity of the mixture. The mixture delivered by the ca rt buretor will remain the same though the position of the fuel supply tank is varied as vmuch as two feet above or two feet below the plane of the carburetor. A I

In the construction of this carburetor I have mmade use of the suction multiplying properties of the Venturi-tube to offset the decrease in volumetric efficiency which would otherwise result from the maintenance at the carburetor of a sufficient suction for lifting fuel to a height of 30 from the low level source of supply.

Sufficient suction or reduction of pressure is maintained at all times and under all engine conditions for lifting fuel the required height without the sacrifice of power at wide open throttle. The venturi is soldesigned and employed' in the carburetor that it roduces the necessary fuel lifting suction w en subjected to a comparatively low induction chamber or manifold vacuum. The Venturi tube is continually under the actionA of in` duction chamber depression and'thereby in,

sures the delivery of fuel for alloperating requirements whether wide open throttle,

'partly open throttle or idlig.

` illustrated in Fig. 1;

lig 3 is a sectional view along the line 33 of .Fig 2; Fig. 4 is a side elevation of a portion of the carburetor showing the intake orifice of the Venturi tube and shutter plate, and

Fig. 5 is a view of a chassis showing the,

installation of myimproved fuel feed carburetor.

Referring now to Fig. 1, I employ a body casing 1 havin a primary air intake 2, an induction cham er 3 with a passage 4 therefor arranged for registration with the intake manifold of an linternal combustion engine. A vertically moving air valve 5 is provided within the casing 1 and arranged to cooperate with the valve seat 6 for the purpose of restricting the flow of air into the induction chamber 3 from Vthe primary air passage 2. The lower end of the valve member 5 carries an air piston 7 which is disposed within an air dashpot 8 formed in the lower p or ltion of the casing 1. A compression spring 9' isA provided for normally maintaining the 'valve 5 upon its seat 6.A Means for adjusting the tension of the valve 5 is provided in a counter-acting adjustable spring 10 which bears 'at its upper end upon the stem of the valve 5 at 11 and which has'its -lower end bearing upon a threaded adjustable thumb screw 12. Y Screw 12 is further provided with a resilient locking member 13 for reventing the unintentional rotation thereo Further means for adjusting the tension ofthe valve 5 such as might be 'required during the changes from season to season is suplied by an 'arm 14 which extends radially rom the sleeve 15 in which the screw 12 is held. The sleeve 15. is constructed to slide vertically in the portion 16 of the lower wall of the casing 1. A compression spring 17 normally holds the sleeve .15 in an elevated positlon. The arm 14 rides'at 18 upon an inclined'surface 19 fastened in the lower wall of the casing so that oscillation of the arm 14 as by the movement' of a control wire 20 (see Flg. 2) may vary th'e tension of the counter-acting sprin 10.

Extending throug aside wall of the casing 1 into the induction chamber 3 is a Venturi tube 21 (see Fig. 3) which forms the only jet or nozzle in the carburetor.

S ecial attention is called to the fact that the gfenturi tube, first, is disposed in a plane transverse to that of the axis of the induction chamber or flow of air from the passage through the valve 5. This construction permits fuel to be introduced in a manner hereinafter described, with the least possible resistance, and unlike those types of carburetors in which a vertical nozzle for introduc-- ing a rich mixture of air and fuel is found. Second, the axis lies in a diametrical plane of the induction chamber. I have found by exhaustive experiments that this position of the venturi provides for the most efcient op- `eration thereof. l.

This Venturi tube is designed to produce a vacuum at its throat 22 which at low engine speeds exceeds the induction chamber vacuum by three to one. In other words', atidle or low s ed wide open throttle the induction cham er shows a pressure reduction of about 9 of gasoline, whereas the suction formed at the throat of the venturi reaches about 27 of gasoline. This dierential or ratio decreases as the speed of the motor increases. 'At 200() R. P. M. wide open throttle, for example, the induction chamber vacuum reaches about 30 of gasoline and the Venturi throat slightly more than 38". i

The throat 22 of the Venturi tube is rovided with a plurality of fuel holes 23 w ich are comparativelyy large, thereby eliminating the possibility of clogging. Provision of these large holes is made possible by the fact that they are not called upon to meter or restrict the flow of gasoline for proper mixtureproportioning. Metering of fuel is brought about by other means presently described.

the fuel as it enters the chamber through the feed passage 31.

Forming the top wall of the chamber 26- is a thin metallic diaphragm l32, the upper side of which is subjected to atmospheric pressure. When the -pressure within ythe chamber 26 is that of the atmosphere the valve 27 is closed and there is a very slight clearance between the valve and the diaphragm.

The diaphragm 32, fuel valve 27 and the spring 29.so cooperate with the venturi to phragm in close engagement with the adj acent wall of the chamber 26 at its periphery, thus maintaining the diaphragm taut.

A cylinder 34 is formed in the upper wall of the cover `32 and a piston 35 is disposed within the cylinder. The cover 33Y is further provided with a passage 36 therethrough connecting the cylinder with the chamber 26 above thendiaphragm. A compression spring 37 tends to hold piston l35 in an elevated position.

The piston 35 forms with the cylinder 34 anaccelerating means for causing momentarily a relatively rich mixture of fuel upon the sudden downward movement of the pisf ton. Such momentary enriching of the fuel mixture is necessary whenever the throttle is quickly opened from idle position and to insure the automatic operation of the accelerator piston a bell crank 38 is mounted at 39 upon the casing 1 and has one end connected with the'piston and its opposite end provided with a roller 41 which rides upon a cam 42 carried by the shaft 430i the induction passage throttle valve 44. It will thus be seen that upon the opening of the throttle the depression of the piston will be caused and consequently a rise in pressurevabove the diaphragm results `to move the Valve 27 to a greater open position than existing at the time. Under normal running conditions the clearance between the piston 35 and the cylinder 34 permits atmospheric pressure above the diaphragm.

Mounted upon the throttle shaft 43 and arranged to extend over the inlet orifice 45 of the Venturi tube 21 is a shutter plate or economizer 46. This Shutter serves the function of restricting the ow of air through the venturi and thereby controlling the amount of suction produced at the throat thereof. In a venturi such as used on this carburetor the highest efficiency or in other Wordsv the highest throat vacuum is attained when there is present a free and unrestricted iow of air through the venturi. If this flow of air is restricted, the throat vacuum drops correspondingly until the point where throat vacuum equals that of induction chamber depression. Obviously when this happens there can be no fuel delivery.

The outermost edge of the shutter 46 is i1'- regular in contour, having its outermost portion at 47 so formed as to lie in registration with the axis of the venturi when the throttle 44 is opened to that extent necessary to cause movement of the vehicle through speeds between ten and forty miles per hour on good miV that the shutter plate '46, does not contactat any time with the adjacent face or end of the venturi 21 but is spaced at a slight distance' therefrom. I have found that by so disposing the plate with respect to the venturiV that the formation of eddies in the orifice of the venturi is less apt to occur than where the shutter is moved in Contact with the end of the venturi to restrict the orifice 45.

Means for maintaining the plate 46 in definite spaced relationship with the outer face 'or end of the venturi is provided in a spacer plate 48 which is fixed with respect to the plate 46 which contacts with the outer face or end of the venturi. A set screw 49 and arcuate slot 50 in the plate 46 serve to permit adjustments of the plate 46 with respect to the throttle shaft 48.

n' explanation of the operation of this carburetor, let us assume the device is mounted for operation on anengine with the throttle 44 opened to a degree permitting the car speed of approximately 20 miles per hour. A suction or pressure reduction is created in the induction chamber 3. This suction is of course formed by the action of the air valve 5 and measures about 20 of gasoline by manometer test. The differential in pressure between atmosphere and induction chamber causes the air to fiow through the Venturi tube 21, thereby producing a suction at its throat which is in excess of 30 of gasoline measured in a manometer tube. This increased suction is communicated directly to the under side of the diaphragm 32.

rIlhe diaphragm 32, fuel valve 27 and spring 29 are so adjusted that when a suction equivalent to 30 of gasoline is formed in the fuel chamber 26, the diaphragm is depressed by atmospheric pressure, thus opening the fuel valve against the tension of the sprin 29. Fuel communication is thereby established between the Venturi tube, and the main fuel supply tank 54 of the Vehicle. The vent provided in the main fuel tank maintains the fuel therein under atmospheric pressure at all times.

It is apparent from the foregoing that fuel is delivered into the throat of the venturi where it is mixed with air flowing thereto. A second mixing takes place when the first rich mixture of fuel and air is delivered into the induction chamber. Here the primary mixture enters the stream of air flowing upwardly around the valve 5 and passes on through the manifold and into the various cylinders of the en lne.

The quantity of el which is delivered into the induction chamber of the carburetor depends upon the differential or difference in pressure which exists between the fuel valve 27 and the Venturi' throat.

If the suctionv is increased at the Venturi throat, leaving the restriction of the fuel valve l27 constant,

there is an increase in the flow of fuel. Con- Versely, if the suction is decreased the mixture then becomes lean. If a less restriction is obtained at the fuel valve 27, leaving the venturi action constant, the mixture is enriched and the mixture is made lean by placing a greater restriction at the fuel valve 27.

It is therefore apparent that the lamount of fuel delivered at the Venturi nozzle into the induction chamber is entirely dependent 'upon the differential existing between the nQZZle Eand the fuel valve restriction. Let it.be assumed now that the level ofthe fuel is raised to about that of the carburetor, assuming further that in the foregoing the level of fuel in the main supply tank was 20 below the carburetor. Without an automatic regulating means, the mixture delivered under these conditions would be exceedingly rich, but with the diaphragm mechanism which I employ, the mixture proportion remains fixed. With the main tank above the carburetor or at a level higher than that before mentioned, fuel Hows into the fuel chamber with greater ease. A greater flow of fuel into the fuel 'chamber results in an increase of pressure in that chamber because the restriction at the nozzle prevents the withdrawal of fuel from the fuel chamber as rapidly as it has flowed thereto -under these n ew conditions. As this pressure increases the dia-- phragm moves upwardly with the result that the fuel valve is moved toward its seat to form a greater restriction than before. Thus conditions immediately become stabilized and although the pressure in the fuel chamber will be slightlyvless than before, the diifen ence will be so slight that it will have an unnot-iceable effect upon the mixture proportions.

A substantiall constant vacuum in the fuel chamber 26 is t ereby automatically maintained by the varying opening of the fuel valve 27 as the fuel chamber vacuum is held substantially fixed regardless 'of fuel supply level. The differential existing between the fuel chamber 26 and the induction chamber 3 remains so nearly constant, a mixture sible speed, the air valve 54 is off its seat andadmitting air into the induction chamber. This is made possible b the fact that the amount of air passing t rough the venturi is neversuiicient for engine operation. *At

this speed and engine condition the economizer shutter 46 is entirely removed from registration with the venturi so that here as in Wide open throttle position, the ven-A 'turi nozzles may deliver thatl rich' mixture which is necessary for best performance. The counteracting spring 10 provides the necessary adjustment for proper idling mixture an is regulated by turning the thumb screw 12.

Referring now to the accelerating means heretofore described. it will be noted that upon sudden opening of the throttle a pressure is applied to the upper side of the diaphragm 32 by the uick descent of the piston 35 in the cylin er 34. As a result of this increased pressure above the diaphragm,

the fuel valve is opened to greater extent than for ordinary running and therefore richer mixture is delivered by the venturi or nozzle. This effect persists only for a few seconds, depending upon the clearance and rateat whichthe pressure is dissipated by leakage between the piston and cylinder walls.

With reference to Fig. l, I have found tha-t a rib 52 formed onthe inner face of the cover 33 and concentric therewith eliminates the possibility of the buckling of the diaphragm 32 whichv might otherwise occur if by chance a diaphragm is employed which is not uniform in thickness throughout.

In Fig. 5 I have illustrated the relative positions of the carburetor and main supply tank 54 with respect to the motor 53a. 53 represents a chassis frame, and 55 the fuel `feed, line connecting the main supply tank 54 with the port 31 of the carburetor 1. It will be noted that in the resent installation, the entire tank lies low the lplane of the carburetor. j Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination ina carburetor of an induction chamber, a Venturi tube project- 2. The combination in a carburetor of an induction chamber, a Venturi tube projecting into said chamber, a fuel passage for conducting fuel to the throat of said venturi,

and a plate disposed in a plane perpendicular .to the axis of said venturi and at a predetermined spaced distance from the adj acent air inlet end of the venturi and arranged for movements in that plane, said plate being further provided with an irregular edge which overlies the orifice of the venturi upon movement' of the plate to control the quantity of air admitted to the venturi.

3. The combination in a carburetor of an induction chamber, a throttle for said induction chamber, a Venturi tube projecting into said chamber, a fuel passage for conducting fuel tothe throat of said venturi, and a plate disposed in a plane perpendicular to the axis of said venturi at a predetermined spaced distance from the adjacent air inlet end of the Venturi and arranged for movement in that plane, said plate being further provided with an irregular edge whichoverlies the orifice of the 'venturi upon movement of the plate to control the quantity of air admitted to the venturi, said plate being connected with ysaid throttle and actuated in its -movement thereby.

4. The combination in a carburetor of an induction chamber, a throttle for said in- `ment in that plane, said plate being further provided with an irregular edge which overlies the orifice of the venturi upon movement of the plate to control the quantity of air admitted to the venturi, said plate being con nected with said throttle and actuated in its of said venturi and at a predetermined distance from the adjacent air inlet end of the venturi and arranged for movement in that plane, said plate being further provided with an irregular edge which ,overlies the orifice A of the venturi upon movement of the plate to control the quantity of air admitted to the .5venturi.

6. The combination in a carburetor of an induction chamber, a throttle for said chamber, a Venturi tube projecting into said chamber, a fuel chamber, a fuel passage for 10, admitting fuel to the throat of said venturi, suction operated means for controlling the passage of fuel from said fuel chamber to the fuel passage, and a plate disposed in a plane perpendicular to the aXis of said venturi at a predetermined distance from the adjacent air inlet end of the venturi and arranged for movement in that plane, said plate being further provided with an irregular edge which may overlie the orifice of the venturi whereby movement of the plate will control the quantity of air admitted to the venturi, said plate being connected with said throttle and actuated in its movement thereby.

7 The combination in a carburetor of an induction chamber, a Venturi tubev projecting into said chamber, a fuel chamber, a fuel passage vfor admitting fuel to the throat of said venturi, suction operated means for controlling the passage of fuel to the fuel passage from said chamber, a plate disposed in a plane perpendicular to the axis of said venturi and at a predetermined distance from the adjacent edge of the venturi and arran ed for movement in that plane, said plate bemg further provided with an irregular edge which may overlie the orifice of the venturi whereby movement of the plate may control the quantity of air admitted to the venturi, and acceleration means operable by said throttle for influencing said suction operated means when said throttle is quickly opened to ca-use an increased iiow of fuel to the fuel passage. 8. The combination in a carburetor of an induction chamber, a Venturi tube projecting into said chamber, a fuel chamber, a fuel passage for admitting fuel to the throat of said venturi, suction operated means for conf trolling the passage of fuel to the fuel passage from said chamber, a plate disposed in a plane perpendicular to the axis of said Venturi at a predetermined distance from the adjacent edge of the venturi andarranged for movement in' that plane, said plate being further provided with an irregular edge which may overlie the orifice of the venturi whereby movement of the plate may control 4the quantity of air admitted to the venturi, acceleration means operable by said throttle for influencing said suction operated means when said throttle is quickly opened tovcause an increased flow of-fuel to the fuel passage, and a spring actuated air valve for controlling the admission of air to said induction chamber whereby the induction chamber depression may remain substantially constant.

9. The combination in a carburetor of an induction chamber, a Venturi tube projecting into said chamber, a fuel chamber, a fuel passage for admitting fuel to the throat of said venturi, suction operated means for controlling the passage of fuel to the fuel passage from said chamber, a plate disposed in a plane perpendicular to the aXis of Said venturi at a predetermined spaced distance from the adjacent edge of the venturi and arranged for movement in that plane, said plate being further provided withan edge formed to variably overlie the orifice of the venturi Whereso; by movement of the plate may control the quantity of air admitted to the venturi, acceleration means operable by said throttle for imiuencing said' suctionoperated means when said throttle is quickly opened to cause an increased flow of fuel to the fuel passage,

a spring actuated air valve for controlling the admission of air to said induction chamber whereby the induction chamber depresi sion may remain substantially constant, and means for adjusting the spring tensionv of said air valve to vary the induction chamber depression. A

, 10. The combination in a carburetor of an induction chamber, means comprising a v nozzle for admitting fuel to said induction chamber, suction operated means including 4a diaphragm for controlling. the quantity of. fuel admitted to said fuel feed means and other means associated with the suction operated means to affect said diaphragm for momentarily augmenting the low of fuel through said nozzle. f

11. In a carburetor of the character described, an induction chamber, a fuel feed means comprising a nozzle for admitting fuel to said induction chamber, a throttle for con-v trolling the passage of fuel mixture through said induction chamber, suction operated means including a diaphragm for controlling 11o the passage of fuel to said fuel feed means and other means operated by said throttle and associated with said suction means to affect said Adiaphragm for momentarily and uniformly augmenting. the iiow'- of fuel 115 through said nozzle. e, Y

12. The`c'ombination in a carburetor of an induction chamber, fuel feed means for admitting fuel to said chamber, suction operated means including a diaphragm having 120 one side at normally atmospheric pressure for controlling the passagef of fuel to said fuel feed means, and means for momentarily increasing the pressure .onthe atmospheric side of said ldiaphragm to ,cause said suction operated means to admit momentarily a greater quantity of fuel therethrough.

13. The combination in a carburetor of an induction Vchamber fuel feedmeans for admitting fuel to the chamber, suction operated means including a. diaphragmhaving one side subjected to atmospheric pressure for controlling the quantity of fuel admitted to the fuel feed means, a cylinder having a passage communicating with the atmospheric side of said diaphragm, and, a piston in said cylinder wherebysaid operatlon of the piston may increase the pressure on the atmospheric side of the diaphragm to cause` momentarily a greater flow of fuel to the lfuel feed means.

14. The combination in a carburetor of an induction chamber, fuel feed means for admitting fuel to the chamber, a throttle for controlling the passage of fuel mixture through the chamber, suction-.operated means including a diaphragm having one side subjected to atmospheric pressure for controlling the passage of fuel to the fuel feed means, and other means-associated with the throttle and operated thereby for momentarily increasing the pressure on the atmospheric side of said diaphragm to cause a m-omentarily increased iiow of fuel to the fuel means.

15. The combination in a carburetor of an induction fuel'chamber, fuely feed means for admitting fuel to said chamber, a throttle for controlling the passage of fuel mixture therethrough, suction operated means including a diaphragm having one side subjected to atmospheric pressure for controlling the passage of fuel,to said Ifuel feed means, 'a cylinder having a passage communicating withthe atmospheric side of said diaphragm, a piston in 'said cylinder, and means connecting'the piston with said throttle whereby sudden opening of the throttle will cause light -movement of the piston to momentarily increase the pressure on the atdiaphragm, a piston loosely fitted in said cylinder, and means connecting the piston with said throttle whereby sudden opening of the throttle will cause lightmovement of the piston to momentarily increase the pressure on the atmospheric side of the diaphragm and increase the flow of fuel to the fuel feed means.

1n witness whereof, I hereunto subscribe my name this 19th day of October, 1926.

ROBERT F. BRACKE.

mospheric side of the diaphragm Aand ini crease the ow of fuel'to th'e fuel feedmea'nsl. 16. The combination in a carburetor of an induction chamber fuel feed means for admitting fuel to thechamber, suction operated means including a diaphragm having one side subjected to atmospheric pressurev for controlling the quantity of fuel admitted to the fuel feed means, a cylinder vhaving a passage communicating with the atmospheric side'of said diaphragm, anda piston loosely ttedin said cylinder whereby said operation of the piston may increase the pressure on the atmospheric side of the diaphragm to cause momentarily a greater ow of fuel to the fuel feed means. f

17. The combination in a carburetor of an induction fuel chamber, fuel feed means for admitting fuel to said chamber, a throttle forcontrolling the passage of fuel mixture therethrough, suction voperated means including a diaphragm having one side subjected to atmospheric pressure for controlling the passage of fuel to said fuel feed means, a cylinder having a passage communicating vwith the atmospheric side of said 

